(JTA) – Two Palestinian sisters attempting to cross into Israel from the Gaza Strip so that one could receive cancer treatment were caught smuggling explosives.

The explosives, used in the production of homemade bombs, were hidden in tubes carried by the women labeled “medical materials,” the Shin Bet security service said in a statement issued Wednesday evening, hours after the women were stopped at the Erez Crossing.

The sisters were approved for entry into Israel so that one could receive potentially life-saving treatment for her illness.

According to the Shin Bet statement, a preliminary investigation showed that the explosives were sent by Hamas to be used in a terrorist attack on Israeli targets in the “near future.”

The incident “attests to the ongoing efforts by terrorist organizations based in the Gaza Strip, especially Hamas, to exploit Israel’s humanitarian initiatives and the medical assistance that it provides to residents of the Gaza Strip, in order to perpetrate attacks in Israel,” the Shin Bet said.

“To our regret, it has been proven again that Gaza Strip-based terrorists are continuing their efforts to exploit the humanitarian channel in order to carry out attacks in Israel,” he said in a statement. “The security inspectors acted exactly as expected, with exemplary professionalism.”